Five Los Angeles-area residents were indicted, including suspected ringleader Maria "Reyna" Lopez-Diaz, 60, of Compton, California, authorities said. Four were taken into custody Thursday.

Lopez-Diaz and two others are in the country illegally and face possible deportation, the customs enforcement agency said in a statement.

The investigation, which involved several agencies, began in January 2010.

People paid "$2,000 to $4,000 to be smuggled into the U.S." and were locked in trunks or compartments next to loud V8 engines during some of the hottest times of the year, Arnold said.

The scheme sought out "financially disadvantaged U.S. citizens from south Los Angeles who did not speak Spanish, offering them $300 to $800 for every illegal immigrant they successfully transported," the customs enforcement agency said in a news release.

"In the event they were stopped by the Border Patrol, the drivers' inability to speak Spanish and communicate with the aliens they were transporting meant the drivers had limited information about the broader smuggling scheme," the customs enforcement agency said.

Lopez-Diaz is alleged to have purchased smuggling vehicles, recruited drivers and coordinated with international smugglers, all while providing drivers with travel expenses, cars and cell phones.

"Human smuggling is a very low overhead proposition," Arnold said. "So the rest of it is pure profit. Gas from the border to LA (Los Angeles) is not much."

Arnold said that "interviews with cooperators," as well as other "information collected during the investigation," led the authorities to believe the ring was involved in "300 and some runs."

"We arrested a few people," he said. "The ones that were interdicted by the U.S. Border Patrol."

The scheme did not just occur during hot weather. Smuggling routes "over the mountains in east San Diego County" subjected the illegal immigrants to extreme cold and inclement weather, Arnold said.

All five defendants are accused of one count of conspiracy. Other charges against some include transporting illegal immigrants and harboring them, the agency said.

The maximum penalty on each count is 10 years in prison and a $250,000 fine.

"They look at people they smuggle not as people but as commodities and it represents money for them," Arnold said. "If they lose some people, it's just a calculated risk for them; it's just a cost of doing business."